Fps drop in fortnite

[chrisneff1214]

Okay so I'll be playing fortnite getting a solid capped 120 fps then I'll get in a gunfight or build in my FPS drops below 60 into the 50s and it's almost unplayable I am currently running 12 gigabytes of RAM an Athlon 880k Radeon RX 560 and a 500gb hard drive why is this happening I'm getting frustrated also I know my CPU is bottlenecking my gpu

 

[chrisneff1214]

Side note this is new after the update currently